Fluidizing method and apparatus

ABSTRACT

A fluidizing method transports particulates by gravity flow but passes the particulates through a fluidizer which is partitioned by a porous distributor plate to form first and second chambers and wherein the particulate materials pass through said first chamber which is in gaseous communication with said second chamber via the porous distributor plate. Gas is delivered to the second chamber at a pressure sufficient to generate a gas bearing between the porous distributor plate and the particulate material. The gas is permitted to migrate through the particulate material, but it is then vented to the surrounding atomosphere without causing substantial turbulence in the particulate material and to reduce tendencies for dusting and separation of the particulates into sizes.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates in general to a method and apparatus forfluidizing particulate material during delivery to and filling cavitiesin a uniform and consistent manner during successive filling operations.The invention relates in particular to powder delivery systems fordelivering particulate material and filling closed cavities, such as diecavities of die-casting machines, and for filling open cavities, such ascontainers on food packaging production lines.

[0003] 2. Description of the Related Art

[0004] Powder delivery systems are used for delivering particulatematerial and filling die cavities of, e.g., die-casting machines priorto powder compaction in processes for fabricating consolidated part forautomotive, aerospace, micro-electronics, pharmaceuticals, vitamins,etc. Powder typically is gravity-fed from a main hopper to the diecavity by transfer through a flexible tube to a feedshoe or fillshoe,which deposits powder into the die cavity. The process of depositingpowder in the die cavity is called “die filling.”

[0005] The process of powder delivery and filling by gravity is the mostcommon way of delivering powder and filling a die cavity. The feedshoeis pushed forward between the surface of the die cavity and a top punch,and positioned on top of the die cavity. Depending on powder flowcharacteristics, cavity shape and size, type of die-casting machine, andfilling method, the feedshoe is typically mechanically vibrated while ontop of the die cavity to loosen the powder, break any clumps and ensurethat the die cavity is full before the feedshoe is retracted.

[0006] There are several problems associated with prior art processesfor powder delivery and filling of a die cavity.

[0007] One such problem is variation in filling conditions duringsuccessive filling operations, i.e., from part to part. Variations infilling conditions from part to part result in variations in weight frompart to part, and non-uniform fill of the die cavities. A non-uniformfill results in variations in density between the front and back of thepart and in distortion of the part during sintering. Typically, partspecifications include limits on acceptable variations in part weightand on acceptable variations in density within the part. Parts that donot meet the specifications are rejected.

[0008] The variations in filling conditions from part to part are due,in part, to variations in head pressure, clumping, surge, and dead zonesof material within the feedshoe. The head pressure is due to the powderin the feedshoe, the flexible tube and the main hopper. As a result ofthe powder delivery system design, wherein the flexible tube istypically connected to the backside of the feedshoe, the powder in theback of the die cavity is subjected to a higher head pressure than thefront of the die cavity.

[0009] During operation, the feedshoe is pushed forward and centeredabove the die cavity and then retracted before compacting. The movementof the feedshoe across the die cavity results in the back of the diecavity being subjected to the higher head pressure for a longer periodof time than the front of the die cavity. These effects combine toproduce variations in part density between the back and the front of thepart, which result in distortion during sintering.

[0010] Clumping and surge of the powder within the feedshoe and flexibletube contributes to non-uniform filling of die cavities. Mechanicalshaking of the feedshoe above the die cavity can break clumping in thepowder and improve fill uniformity but is not consistent duringsuccessive filling operations.

[0011] A further problem results from fine powders/particulatematerials, which do not have good flow characteristics, thus posing aserious problem for the die filling operation. Lubricants are added toreduce interparticle friction and improve flowability, thereby requiringan energy intensive delubing cycle after compacting to remove all addedlubricants.

[0012] A further problem is that mechanical shaking of the feedshoecauses segregation of fine powders/particulate materials from coarsepowders/particulate materials resulting in a loss of uniformity inparticle size distribution and chemical composition. This powdersegregation results in powders with different apparent densities andchemical composition being filled in the die cavity during successivepowder filling operations.

[0013] A solution to these and other problems is needed. Such solutionis provided by the novel invention recited herein.

BRIEF SUMMARY OF THE INVENTION

[0014] The invention contemplates supplying a technique and apparatusfor delivering particulate material and filling cavities in a uniformand consistent manner during successive filling operations. In preferredembodiments, the invention provides a powder delivery system fordelivering particulate material and filling closed cavities, such as theclosed die cavities of die-casting machines; or for filling opencavities, such as open containers on food packaging production lines.

[0015] Die Casting and Sintering

[0016] The three basic steps for producing parts by the press and sinterprocess are mixing, compacting and sintering. In step one, mixing,elemental or prealloyed powders are mixed with lubricants or other alloyadditions to produce a homogeneous mixture of ingredients. The lubricantreduces interparticle friction and improves the flow characteristics ofthe powder mixture. In step two, compacting, mixed powder is fed into aprecision die on a die-casting machine and is compacted. Compacting theloose powder produces a “green compact” which has the size and shape ofthe finished part when ejected from the die. In step three, sintering,the green compacts are placed on a wide-mesh belt and slowly movedthrough a controlled atmosphere furnace. The parts are heated to belowthe melting point of the base material, held at the sinteringtemperature, and then cooled.

[0017] Tabletting and Dry Compaction

[0018] The production of pharmaceutical preparations, e.g., vitamins, ortablets containing an active medicament in a carrier or other suitableexcipient, requires precise and homogeneous mixation techniques.Similarly, candies usually must have an acceptable hardness, mouthfeel,and duration within the mouth. These characteristics can depend in partupon the homogeneity of the composition in the tablet form.

[0019] Dry powder, or a semidry paste, is placed within a tablet moldand subjected to pressure. The amount of pressure usually determines thehardness of the tablet, and consequently its lifetime within the mouth(subject, of course, to chewing). It is important for dosage amount andappearance that the powder feed correctly into the tabletting machine.

[0020] The Closed Cavity Device

[0021] In one embodiment, the invention provides a method and apparatusfor powder delivery and filling of a closed cavity, such as a die cavityof a die-casting machine. The apparatus includes a mini-hopper, atransport device, a delivery chute and a gas control unit.

[0022] The mini-hopper has a porous distributor plate for partitioningthe mini-hopper into a first partition in which the bed of particulatematerial is stored and a second partition separate from the firstpartition and in communication with the first partition via the porousdistributor plate. An inlet port is provided for receiving a compressedgas in the second partition at a low pressure, whereby only the bottomsurface of the bed of particulate material becomes fluidized bymigration of the compressed gas through the porous distributor plate andinto the first partition.

[0023] The transport is connected to the side of the mini-hopper anddelivers powder/particulate material from the mini-hopper to thedelivery chute. The transport has a porous distributor plate forpartitioning the transport into a first partition in which theparticulate material flows and a second partition separate from thefirst partition and in communication with the first partition via theporous distributor plate.

[0024] The delivery chute can function as the powder discharge unitdirectly above the die cavity. Fluidizers are embedded in the deliverychute to ensure that powder is fluidized before filling the die cavity.The delivery chute is customized to part shape to optimize fillperformance for individual parts or a family of parts, depending on partsize and shape complexity.

[0025] An in-line dryer may be provided to remove moisture from the gassupply, while an in-line filter may be used to remove solid impuritiesin the gas supply. The gas control unit can include three independentpressure regulators, located in a separate housing, and three pneumaticsolenoids, which are used to regulate the flow of gas to each segment ofthe fillshoe independently. The solenoids are preferably timed tocontrol fluidization of the powder over the die cavity.

[0026] The apparatus in one embodiment provides for venting of gas ineach segment of the fillshoe to prevent build up of pressure within thesystem and in the die cavity, which will prevent uniform, complete andconsistent filling of die cavities. The apparatus also preferablyprovides for collection of any fine powder particles that may escapethrough the venting screens.

[0027] The apparatus in a particularly preferred embodiment has a lowprofile, fits on a compacting press, and can be pushed into positionbetween the die surface and top punch of a die-casting machine duringdie filling operation.

[0028] The apparatus for filling closed cavities is preferably easilymovable. The apparatus is pushed forward into position above a diecavity for filling and then retracted after filling and beforecompacting. The low profile apparatus for filling closed cavities can bepositioned between the die surface and top punch of a die-castingmachine.

[0029] The Open Cavity Filling Device

[0030] The invention, in another preferred embodiment, provides a methodand apparatus for powder delivery and filling of an open cavity, such asa container on food packaging production lines. The apparatus forfilling open cavities is preferably stationary, although it may be movedfor adjustment purposes or to accommodate packagings of various sizes ona continuous production line.

[0031] The apparatus in one embodiment includes a mini-hopper, atransport, a delivery chute and a gas control unit.

[0032] The mini-hopper can function as an intermediate storage unit forpowder and is configured to receive powder from the main hopper. Themini-hopper has specially designed porous distributor plates forpartitioning the mini-hopper into a first partition in which the bed ofparticulate material is stored and a second partition separate from thefirst partition and in communication with the first partition via theporous distributor plate.

[0033] An inlet port is provided for receiving a compressed gas in thesecond partition at a low pressure, whereby only a layer of particulatematerial next to the porous distributor plates becomes fluidized bymigration of the compressed gas through the porous distributor platesand into the first partition.

[0034] The transport delivers powder/particulate material from themini-hopper to the delivery chute. The transport has a porousdistributor plate for partitioning the transport into a first partitionin which the particulate material flows and a second partition separatefrom the first partition and in communication with the first partitionvia the porous distributor plate. An inlet port is provided forreceiving a compressed gas in the second partition at a low pressure,whereby only the bottom layer of the particulate material becomesfluidized by migration of the compressed gas through the porousdistributor plate and into the first partition.

[0035] The delivery chute preferably has a center fluidizer which isused to regulate powder flow and meter the amount of powder. This can beaccomplished, e.g., by the use of a timer and turning the gas flow onand off. The delivery chute can act as a fluidized powder valve bypreventing powder flow once the gas is turned off.

[0036] The gas control unit is used to control the gas moisture contentand regulate powder fluidization and powder flow in relation to themovement of the production/filling line.

[0037] In a preferred embodiment, an in-line dryer removes moisture fromthe gas supply. An in-line filter is also preferably used to removesolid impurities in the gas supply. The gas control unit is used tocontrol the gas moisture content and regulate powder fluidization inrelation to the movement of the production line.

[0038] The gas control unit in one embodiment includes three independentpressure regulators, located in a separate housing, and three pneumaticsolenoids, which are used to regulate the flow of gas to each segment ofthe fillshoe independently. The solenoids are timed to controlfluidization of the powder over the open container on a production line.When the gas to the fluidized powder valve is turned on, particulatematerial flows into the open container. When the gas to the fluidizedpowder valve is turned off, the flow of particulate material is cut-offimmediately.

[0039] A timer is preferably used to regulate the time at which the gasto the fluidized powder valve is turned on and off, providing anaccurate way of metering particulate material for filling a container oran open cavity.

OBJECTS OF THE INVENTION

[0040] It is therefore an object of this invention to provide a newmethod and apparatus for powder filling of a die cavity.

[0041] It is a further object of this invention to provide an apparatuswith a low profile that can be fitted on a die-casting machine betweenthe die surface and the top punch of the die-casting machine.

[0042] It is a further object of the invention to provide a method andapparatus for powder delivery and consistent filling of a die cavityfrom the feedshoe during successive filling operations.

[0043] It is a further object of the invention to provide a method andapparatus for powder delivery and consistent filling of a die cavitywhich improves uniformity of fill of the die cavity from the feedshoe.

[0044] It is a further object of the invention to provide a method andapparatus for powder delivery to a die cavity which reduces oreliminates segregation of fine particles from coarse particles and whichmaintains uniformity in chemical composition.

[0045] It is a further object of the invention to provide a method andapparatus for powder delivery and filling of a die cavity which enhancesthe flowability of fine powders/particulate materials.

[0046] It is a further object of the invention to provide a method andapparatus for powder delivery and filling of a cavity for formingtablets, which apparatus enhances the flowability of finepowders/particulate materials.

[0047] It is a further object of the invention to provide a method andapparatus for powder delivery and filling of a die cavity which reducesor eliminates the need for using organic binders to adhere the fineparticles with the coarse particles to prevent particle segregation.

[0048] It is a further object of the invention to provide a method andapparatus for powder delivery to a die cavity, which minimizes oreliminates the need to use a lubricant.

[0049] The foregoing and other objects, features, and advantages of theinvention will be apparent to the skilled artisan having regard for thisdisclosure. The examples which follow are intended to serve asillustrative and not by way of limitation.

BRIEF DESCRIPTION OF THE DRAWINGS

[0050]FIG. 1A shows a cross-sectional view of an exemplary apparatus forfilling closed cavities according to a preferred embodiment.

[0051]FIG. 1B is a schematic diagram of an exemplary apparatus for a gascontrol unit of an apparatus for filling closed die cavities.

[0052]FIG. 2A is a top plan view of an examplary delivery chute designwith multiple fluidizers or pedals.

[0053]FIG. 2B is a cross-sectional view of an exemplary chute designwith multiple fluidizers or pedals.

[0054]FIG. 2C is a cross-sectional view of an individual fluidizer.

[0055]FIG. 3 is a cross-sectional view of another exemplary deliverychute design with a ring fluidizer.

[0056]FIG. 4A is a cross-sectional view of another preferred embodimentof a delivery chute design with a ring fluidizer and a center fluidizerillustrating a gas off condition whereby the chute functions as apassive valve (powder locks when gas is off.

[0057]FIG. 4B is a cross-sectional view of the embodiment of FIG. 4Aillustrating the gas on condition whereby the delivery chute functionsas a passive valve (powder flows when gas is on).

[0058]FIG. 5A is a cross-sectional view of an embodiment of theinvention configured for filling open cavities, showing the powder lockwhen the gas is off.

[0059]FIG. 5B is a cross-sectional view of an embodiment of theinvention configured for filling open cavities, showing the powderflowing when the gas is on.

[0060]FIG. 6 is a cross-sectional view of an embodiment of the inventionconfigured for filling open cavities with powders with good flowcharacteristics.

[0061]FIG. 7 is a cross-sectional view of an embodiment according to theinvention for filling open cavities with powders with poor flowcharacteristics.

[0062]FIG. 8 is a cross-sectional view of a fluidized in-line connectoraccording to the present invention to assist the flow of powders withpoor flow characteristics.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0063] The following description of preferred embodiments is meant to beread in conjunction with the accompanying drawings, in which referencecharacters refer to the same parts throughout the various views. Thedrawings are not necessarily to scale, emphasis instead is being placedupon illustrating principles of the invention. The drawings serve merelyto illustrate the invention, and are not meant to limit it in scope inany way.

[0064] The present invention provides a method and apparatus for powderdelivery and filling of cavities in general, said cavities being usedfor sintering, casting, die casting, tabletting, or other forms ofpowder use including metallurgy, or other industrial, manufacturing,distributing, or other uses. For ease of description, the belowoccasionally references a preferred embodiment, pressing and sintering,but it is clear to the skilled artisan that many uses for the instantinvention will be apparent without departing from the spirit and claimsof the instant disclosure.

[0065] Powder Processes Generally

[0066] There are three basic steps for producing parts by a technique ofpressing, or pressing and sintering.

[0067] Initially, the components of the composition to be made into apart are mixed. Mixing should be uniform to ensure that the resultantpart has a homogeneous structure and no large agglomerations ofparticles or voids are present. The components may be powders, granules,prealloyed particulates, particles made by any of several knowntechniques—air atomization, water atomization, or the like.

[0068] The components may be uniform or irregular; in any event theprimary object is to ensure a uniform dispersion, while mixing and alsowhile being transported to the die casting machine. In this step,mixing, elemental or prealloyed powders may be mixed with lubricants orother alloy additions to produce a homogeneous mixture of ingredients.The lubricant reduces interparticle friction and improves the flowcharacteristics of the powder mixture.

[0069] The powder or the like is then subjected to compacting, whereinmixed powder is fed into a rough cut or precision die on a die-casting,tabletting, or other machine and is compacted. Compacting the loosepowder produces a “green compact” which has the size and shape of thefinished part when ejected from the die. It is important that thecomponent powder subjected to the compaction is uniformly distributed inthe die or mold and homogeneous. If a tablet is being produced, this isfrequently the last step if no further processes are necessary, e.g.coating or the like.

[0070] During sintering, the so-called “green compacts” are placed on awide-mesh belt and slowly moved through a controlled atmosphere furnace.The parts are heated to below the melting point of the base material,held at the sintering temperature, and then cooled.

[0071] Other forms of metallurgy, e.g. the production of various alloys;or the production of ceramic metal (cermet) materials, require asimilarly homogeneous dispersion of materials within a binder, lube,other carrier, or no carrier. The apparatus and method of the instantinvention ensures such a dispersion.

[0072] The Closed Cavity Apparatus and Process

[0073] In one version of the invention, the cavity to be filled is aclosed cavity, such as a die cavity of a die-casting machine or thetablet forming plate of a tabletting machine.

[0074] The apparatus contains a mini-hopper, a transport device, adelivery chute and a gas control unit. The mini-hopper may function asan intermediate storage unit for powder and is configured to receivepowder from the main hopper. The mini-hopper provides isolation of thefillshoe from the main powder hopper and regulates powder pressure headduring the filling operation.

[0075] The mini-hopper has a porous distributor plate for partitioningthe mini-hopper into a first partition in which the bed of particulatematerial is stored and a second partition separate from the firstpartition and in communication with the first partition via the porousdistributor plate.

[0076] An inlet port is provided for receiving a compressed gas in thesecond partition at a low pressure, whereby only the bottom surface ofthe bed of particulate material becomes fluidized by migration of thecompressed gas through the porous distributor plate and into the firstpartition.

[0077] The transport is connected to the side of the mini-hopper anddelivers powder/particulate material from the mini-hopper to thedelivery chute. The transport has a porous distributor plate forpartitioning the transport into a first partition in which theparticulate material flows and a second partition separate from thefirst partition and in communication with the first partition via theporous distributor plate.

[0078] The delivery chute may function as the powder discharge unitdirectly above the die cavity. Fluidizers are preferably embedded in thedelivery chute to ensure powder is fluidized before filling the diecavity. The delivery chute is customized to part shape to optimize fillperformance for individual parts or a family of parts, depending on partsize and shape complexity.

[0079] For example, one center fluidizer is used for large ring-shapedparts, and functions as a passive (no moving component) powder valvewhen the gas is turned on and off. Several small fluidizers are used forgear-shaped parts, and are positioned above gear lightening holes. Aring fluidizer is used for powders with poor flow characteristics and toincrease fill speed.

[0080] The gas control unit is used to control the gas moisture contentand regulate powder fluidization in relation to the movement of thefillshoe on the die-casting machine. An in-line dryer preferably removesmoisture from the gas supply, and preferably an in-line filter is usedto remove solid impurities in the gas supply.

[0081] In this embodiment, the gas control unit includes threeindependent pressure regulators, located in a separate housing, andthree pneumatic solenoids, which are used to regulate the flow of gas toeach segment of the fillshoe independently. The solenoids are timed tocontrol fluidization of the powder over the die cavity.

[0082] The apparatus provides for venting of gas in each segment of thefillshoe to prevent build up of pressure within the system and in thedie cavity, which will prevent uniform, complete and consistent fillingof die cavities. The apparatus also provides for collection of any finepowder particles that may escape through the venting screens. Theapparatus has a low profile, fits on a compacting press, and can bepushed into position between the die surface and top punch of adie-casting machine during die filling operation.

[0083] The Open Die or Container Apparatus and Process

[0084] The invention also provides a method and apparatus for powderdelivery and filling of an open cavity, such as a container on foodpackaging production lines.

[0085] The apparatus in this embodiment likewise consists of amini-hopper, a transport, a delivery chute and a gas control unit.

[0086] The mini-hopper again may function as the intermediate storageunit for powder and receives powder from the main hopper. Themini-hopper has specially designed porous distributor plates forpartitioning the mini-hopper into a first partition in which the bed ofparticulate material is stored and a second partition separate from thefirst partition and in communication with the first partition via theporous distributor plate.

[0087] An inlet port is provided for receiving a compressed gas in thesecond partition at a low pressure, whereby only a layer of particulatematerial next to the porous distributor plates becomes fluidized bymigration of the compressed gas through the porous distributor platesand into the first partition. The special design for the porous platesis required because of the very poor flow characteristics of food,vitamins, and similar products.

[0088] The transport device delivers powder/particulate material fromthe mini-hopper to the delivery chute. The transport device has a porousdistributor plate for partitioning the transport into a first partitionin which the particulate material flows and a second partition separatefrom the first partition and in communication with the first partitionvia the porous distributor plate.

[0089] An inlet port is provided for receiving a compressed gas in thesecond partition at a low pressure, whereby only the bottom layer of theparticulate material becomes fluidized by migration of the compressedgas through the porous distributor plate and into the first partition.

[0090] The delivery chute has a center fluidizer which is used toregulate powder flow and meter the amount of powder with the use of atimer and turning the gas flow on and off. The delivery chute acts as afluidized powder valve.

[0091] The gas control unit is used to control the gas moisture contentand regulate powder fluidization and powder flow in relation to themovement of the production/filling line. Preferably, an in-line dryerremoves moisture from the gas supply and an in-line filter is used toremove solid impurities in the gas supply.

[0092] The gas control unit in this embodiment is used to control thegas moisture content and regulate powder fluidization in relation to themovement of the production line. The gas control unit includes threeindependent pressure regulators, located in a separate housing, andthree pneumatic solenoids, which are used to regulate the flow of gas toeach segment of the fillshoe independently.

[0093] The solenoids are timed to control fluidization of the powderover the open container on a production line. When the gas to thefluidized powder valve is turned on, particulate material flows into theopen container. When the gas to the fluidized powder valve is turnedoff, the flow of particulate material is cut-off immediately. A timer isused to regulate the time at which the gas to the fluidized powder valveis turned on and off, providing an accurate way of metering particulatematerial for filling a container or an open cavity.

[0094] Detailed Description with Reference to the Drawings

[0095] In the following description, the following definitions andexplanations apply.

[0096] A closed die cavity refers to an embodiment set up such thatthere is no gap or open space between the apparatus forpowder/particulate material filling and the die cavity receiving thepowder/particulate material.

[0097] A fillshoe is a device to which powder/particulate material isdelivered in order that the die cavity or other mold may be filled.

[0098] In use, the fillshoe is held tight against the die surface (nogap is allowed) and the powder/particulate material is dropped into thedie cavity.

[0099] To accomplish this action, the fillshoe moves in a translatorymotion (back and forth) above the die cavity and therefore is sizelimited such that it fits between the die surface and the top punch of adie-casting machine during the fill operation.

[0100] With particular reference to FIGS. 1A and 1B, a powder deliveryand filling system includes a mini-hopper 10, a transport device 12, adelivery chute 14 and a gas control unit 16. The mini-hopper 10 has aporous distributor plate 18 for partitioning the mini-hopper into afirst partition 20 in which the bed of particulate material is storedand a second partition 22 separate from the first partition and incommunication with the first partition via the porous distributor plate18.

[0101] An inlet powder port 24 is provided for receiving powdermixture/particulate material in the first partition 20. The inlet powderport 24 is connected to the main hopper 26 with a flexible tube 28. Thepowder flows from the main hopper 26, through the flexible tube 28,through the inlet powder port 24 into a leveling pipe 30, and thenceinto the first partition 20 of the mini-hopper 10.

[0102] When the powder level in the mini-hopper 10 reaches the base ofthe leveling pipe 30 the powder forms a lock, powder flow stops and thepowder level remains constant. The powder flow resumes to refill themini-hopper 10 as soon as sufficient powder is discharged from theapparatus into the die cavity 32.

[0103] As such, no metering of the powder into the mini-hopper 10 isrequired and the powder level in the mini-hopper 10 fluctuates somewhatduring the filling operation. It is preferred that the amount of powderstored in the mini-hopper 10 should be equivalent to at least 5 timesthe amount of powder required to fill the die cavity 32, thus assuring aconstant flow.

[0104] An inlet port 34 is provided for receiving a compressed gas inthe second partition 22. The porous distributor plate 18 ensures uniformtransmission of gas pressure to all sections of the mini-hopper 10. Themesh size of the porous distributor plate 18 depends on the particlesize distribution of the powder/particulate material, and is chosen toprevent clogging by entrapment of the small particles within the pores.

[0105] The mesh material is preferably stainless steel to provide highstrength, good wear properties and good weldability, and non-corrosivebehavior. Other materials may be used as well. The powder in themini-hopper 10 is loosened by migration of the compressed gas throughthe porous distributor plate and into the first partition of themini-hopper 10, and depending on the applied gas pressure the powder canbecome fluidized.

[0106] The bottom surface of powder in the mini-hopper 10 is loosenedfirst and, as the pressure of applied gas rises becomes fluidized. Asthe amount of pressure is increased, all powder in the mini-hopper 10can be fluidized. The amount of fluidization is controlled by regulatingthe gas pressure to the inlet gas port 34.

[0107] The proper regulation of the applied gas pressure and flow isimportant to the proper performance of the fill system. In the mostpreferred embodiment of this invention, only the bottom surface (or thinlayer) of powder is loosened or fluidized. This layer will then providea “gas bearing” which reduces friction and increases powder flow rate.

[0108] The gas pressure used depends on the powder characteristics andshould be kept at a minimum. Metal powders typically used in the powdermetallurgy industry have admixed lubricants and can be characterized ashaving good flow characteristics. For these powders the applied gaspressure used in the first partition of the mini-hopper 10 is less than5 psi, typically around 2 psi.

[0109] For fine powders with poor flow characteristics, the magnitude ofthe applied gas pressure should be increased, typically up to 10 or 15psi depending on powder characteristics, but care should be exercised tokeep the applied gas pressure to a minimum necessary to accomplish thefunction of loosening the lowermost layer.

[0110] It should be noted that the pressures are applied pressures onthe upstream side of the porous distributor plate 18. The actual gaspressure seen by the powder is less than the applied pressure because ofa pressure drop across the porous distributor plate 18. The gas pressureis also adjusted to control the flow rate of powder out of themini-hopper 10.

[0111] The use of low gas pressure ensures that only the bottom layer ofthe powder bed stored in the mini-hopper 10 is fluidized while themajority of the powder bed remains in a solid state. The use of low gaspressure will prevent powder segregation in the mini-hopper 10 whenusing a powder mixture or alloy with a wide powder size distribution,prevent any dusting of fine particles, and the powder can maintain alock around the inlet leveling pipe 30.

[0112] The use of high gas pressure results in fluidization of theentire powder bed which will cause powder segregation, dusting of finepowders, and prevent a powder lock around the inlet leveling pipe 30which will cause malfunctioning of the fillshoe. The powder flow rateinto the transport 12 can also be controlled by the inclination of theporous distributor plate 18, shown horizontal in FIG. 1A.

[0113] Adding a slope to the porous distributor plate 18 will increasethe powder flow rate out of the mini-hopper 10 and prevents any deadzones of powder in the back of the mini-hopper 10. The inclusion of aslope in the porous distributor plate is most helpful forpowders/particulate materials with poor flow characteristics. Theinclination should be kept small (e.g. between 0 and 20 degrees ofinclination, preferably between 510 degrees, most preferably about 7.5degrees) because a large inclination will cause uneven loosening andfluidization of the layer of powder near the porous distributor plate18.

[0114] The mini-hopper 10 is covered with a venting screen 36, whichallows the gas to escape to prevent build up of pressure within themini-hopper 10 while entraining any particles. The mesh size of theventing screen 36 depends on the particle size distribution of thepowder/particulate material being used.

[0115] The height of powder in the mini-hopper 10, reference letter “H”in FIG. 1A, influences the flow rate of powder into the transport 12. Ata constant gas pressure, the higher the level of H, the higher thepowder flow rate.

[0116] The mini-hopper 10 provides a break between the fillshoe and themain hopper 26. As such, it provides higher efficiency and accuracy offilling by isolating the filling operation from the main powder supplyin the main hopper 26, from variations in head pressure in the flexibletube 28 and main hopper 26, and from powder surge in the flexible tube28. The result is to maintain the same conditions for successive filloperations, which contributes to consistency of fill of die cavity.

[0117] The transport device 12 receives powder from the mini-hopper 10and is connected to the side of the mini-hopper 10 via side discharge38. The side discharge 38, as opposed to a discharge from the base,helps to keep the profile of the apparatus to a minimum to meet theclearance requirements for installation and operation on a die-castingmachine.

[0118] The transport device 12 has a porous distributor plate 40 forpartitioning the transport device 12 into a first partition 42 in whichthe particulate material flows and a second partition 44 separate fromthe first partition and in communication with the first partition viathe porous distributor plate 40. The powder flows from the mini-hopper10 into the first partition of the transport device 12. The powder flowstops when the transport 12 is full.

[0119] The powder flow resumes as soon as powder is discharged from thedelivery chute 14 into the closed die cavity 32. An inlet gas port 46 isprovided for receiving a compressed gas in the second partition. Theporous distributor plate 40 ensures uniform transmission of gas pressureto all sections of the transport 12.

[0120] The powder is loosened and can become fluidized by migration ofthe compressed gas through the porous distributor plate and into thefirst partition. The mesh size of the porous distributor plate 40 againdepends on the particle size distribution of the powder/particulatematerial, and is chosen to prevent clogging by entrapment of the smallparticles within the pores.

[0121] The degree of fluidization is controlled by regulating the gaspressure to the inlet port 46. The pressure and volumetric flow of thegas is critical to the proper performance of the fill system. The gaspressure used in the transport 12 is the same or similar to the pressureused for the mini-hopper 10, and the pressure and volumetric flow arekept at a minimum.

[0122] Again, the use of low gas pressure ensures that only the bottomlayer of the powder in the transport device 12 reaches a fluidized statewhile the majority of the powder remains solid. This will prevent powdersegregation in the transport device 12 when using a powder mixture oralloy with a wide powder size distribution, and prevent any dusting offine particles.

[0123] The transport device 12 is covered with a venting screen 48,which allows the gas to escape to prevent build up of pressure withinthe transport 12 while entraining any particles. The mesh size of theventing screen 48 depends on the particle size distribution of thepowder/particulate material being used. The venting screen extends overthe entire length of the transport 12 to minimize the time required forgas to escape and minimize any disturbance of the powder flow.

[0124] The transport device 12 sits preferably at an angle of about 45degrees to the horizontal. Other configurations are possible, includingfrom 0-15 degrees, 15-30 degrees, 30-45 degrees, and 45-60 degrees.Inclinations beyond 60 degrees are possible, but will require a largeclearance between the die surface and upper punch.

[0125] This angle controls the powder trajectory as it enters thedelivery chute 14. This angle can be adjusted to make sure it meets theclearance requirements of the die-casting machine on which the systemwill be mounted. As such, it can in some embodiments vary from zero,i.e., horizontal, to around 50 degrees. The angle of the transportdevice 12 to the horizontal influences the flow rate from the transportdevice 12 through the delivery chute 14 and into the die cavity 32.

[0126] For the same head pressure, a high angle for the transport device12 will increase the flow rate while a low angle will reduce the flowrate. The angle of the transport device 12 is tailored to powder type.Typically, powders with poor flow characteristics or high angle offriction require a higher angle for the transport device 12.

[0127] The gas pressure at inlet port 46 is also used to control theflow rate. An increase in gas pressure will result in an increase inpowder flow rates and vice versa. The applied gas pressure is adjusteddepending on, inter alia, the cross-sectional area of the transportdevice 12, the cross-sectional area of the die cavity opening, thevolume of the die cavity 32, and the time allowed for fill during thecompacting operation. In addition, the width of the transport device 12is tailored such that the width increases slightly from the mini-hopper10 to the delivery chute 14. The increase in width results in adiverging channel for powder flow. The result is much improved andconsistent powder flow, especially for powders with poor flowcharacteristics.

[0128] The delivery chute 14 functions as the powder discharge unitdirectly above the die cavity 32. The delivery chute 14 has an outerring 50, which surrounds the opening of the die cavity 20. The deliverychute 14 is covered with a venting screen 52, which allows the gas toescape to prevent build up of pressure within the delivery chute 14while entraining any particles.

[0129] As noted above, the mesh size of the venting screen 52 depends onthe particle size distribution of the powder/particulate material beingused. The venting screen 52 should be proximate to the die cavity 32 toallow the gas to escape in the least amount of time to prevent anyturbulence caused by buildup of gas pressure and delay in die fillingoperation. The size of the venting screen 52 is also maximized tominimize the time required for the gas to escape. The lack of properventing will cause variations in filling and partial filling, especiallyfor powders with poor flow characteristics.

[0130] Fluidizers are preferably embedded in the delivery chute 14 toensure powder is fluidized just before filling the die cavity 32. Thedesign of the fluidizers is customized to part shape to optimize fillperformance for individual parts or family of parts, depending on partsize and shape complexity.

[0131] Turning now to FIG. 2A, several small exemplary fluidizers areillustrated. Those as in FIG. 2A are used for gear-shaped parts, and arepositioned, e.g., above gear lightening holes.

[0132] A ring fluidizer as illustrated in FIG. 3 may be used for powderswith poor flow characteristics to improve fill consistency.

[0133] One center fluidizer is illustrated in FIGS. 4a and 4 b, and canbe used, e.g., for large ring-shaped parts. A unique feature of thiscenter fluidizer is that it acts like a powder valve when the gas isturned on and off. FIG. 4A illustrates the “gas off” situation where thepowder is not flowing, and the backup on the central fluidizer keeps thepowder locked. FIG. 4B illustrates the “gas on” situation where thepowder is flowing by the fluidization action of the gas.

[0134] In addition, a ring fluidizer may be combined with either acenter fluidizer or several small fluidizers to increase fill speed andfurther improve fill uniformity.

[0135] Referring again to FIG. 1, an inlet port 54 is provided forreceiving a compressed gas in the center fluidizer. The delivery chute14 is attached to the transport device 12 by a joint plane 56. Themethod of attachment allows the easy removal of the delivery chute 14and its quick replacement and customization for a different die cavity32.

[0136] Turning to FIG. 1B, it may be seen that the gas control unit 16may be located in a separate housing and is used to control the gasmoisture content and regulate powder fluidization timing in relation tothe movement of the fill shoe on the die-casting machine.

[0137] An in-line dryer 58 may be used to remove moisture from the gassupply. An in-line filter 60 may be used to remove solid impurities inthe gas supply. The gas control 16 contains a control device 62, whichmay be a computing device capable of being programmed for various runprofiles and sensing parameters to control the fluidized particulateflow. The control device may also incorporate a timer, three independentpressure regulators 64, three pressure gauges 66, and three pneumaticsolenoids 68. The gas control unit 16 is used to regulate the flow ofgas to each segment of the fillshoe independently.

[0138] The timing of the gas flow to the center fluidizer is used tocontrol the amount of powder discharged into the die cavity 32. Thetiming may be triggered by a micro-controller on the die casting machineor by a proximity sensor mounted on the die casting machine. The diecasting or other machine may also be connected to the control device 62to provide seamlessly integrated operation.

[0139] The use of 3 independent stages for pressure and timing allowscustomization and tuning of each stage of the system for multipleapplications.

[0140] Returning to FIG. 1, it may be seen that the apparatus alsoprovides an exhaust hood 70 for collection of any fine powder particlesthat may escape through the venting screens. The exhaust hood 70 has avent 72 which is left open or can be connected to a vacuum machine ifthe escape of any amount of particles is considered detrimental to theenvironment.

[0141] The venting screens are designed as removable vents for easymaintenance and cleaning of the apparatus. A hold-down mechanism isattached to the fillshoe to hold the fillshoe tight on the die castingmachine and move the fillshoe forward into fill position and pull itback from under the punch during compacting. The hold-down mechanism maybe attached to the fillshoe at shoulder bolts 74.

[0142]FIG. 2A shows the design for a delivery chute for producing, e.g.a gear, by the process according to the invention with one (1)lightening hole at the center and eight (8) lightening holes around thecircumference. The delivery chute shows the layout, which includes acenter fluidizer 74 and eight fluidizers 76 around the circumference. Anouter ring 82 around the fluidizers inside the delivery chute 14 has aninside diameter larger than the outside diameter of the die cavity 32and surrounds the die cavity 32 when the fillshoe is in the fillposition.

[0143] As the fillshoe is pushed forward into fill position above thedie cavity, the fluidizers will be right above core rods inside the diecavity.

[0144]FIG. 2B illustrates a vertical cross section and shows how thecenter fluidizer 74 and the fluidizers 76 around the circumference aresuspended from a manifold 84 inside the delivery chute 14. A gas port 86is provided to allow gas to flow into the individual fluidizers.

[0145] Turning now to FIG. 2C, it can be seen that each individualfluidizer 88 has a tube 90, which acts as a support and allows gas toflow through, The tube 90 is connected at the base to a cup 92. The cup92 is covered with a porous distributor plate 94, which ensures uniformtransmission of gas to the powder inside the delivery chute 14. The tube90 has holes 96 between the cup 92 and the porous distributor plate 94.The holes 96 are evenly distributed around the circumference of the tube90 to ensure uniform gas pressure inside the chamber between the cup 92and porous distributor plate 94. The tube 90 has threads 98 at the top.The threads 98 are used to suspend the fluidizer 88 from the manifold 84(FIG. 2B). A lock nut 99 at the base of the threads 98 is used to securea tight fit of the fluidizer 88 to the manifold 84.

[0146] The center fluidizer 74 (FIG. 2A) and the fluidizers 76 aroundthe circumference have the same design as discussed for an individualfluidizer 88 (FIG. 2C). The diameter of the center fluidizer 74 can bedifferent than the diameter of the other fluidizers 76, depending on thepart shape.

[0147] A collimator 100 (FIG. 2A) is centered within the delivery chute14 (FIG. 1A) and on the center fluidizer 74 (FIG. 2A). The optimal casefor powder filling is to drop the powder vertically and uniformly abovethe die cavity 32. The powder exits the transport device 12 at an anglealpha and enters the delivery chute 14 through the collimator 100.

[0148] The collimator 100 changes the direction of the powder tovertical. By adjusting the height of the collimator 100 a nearly uniformdistribution of powder is achieved. Without the collimator 100 thepowder exits the transport at an angle and hits the front of thedelivery chute before dropping into the die cavity 32. As a result,without the collimator 100 variations in fill are seen between the frontand back of the die cavity 32.

[0149] Typical operation of the fluidized fillshoe includes severalstages. The fluidized fillshoe shown in FIG. 1A is mounted on a diecasting machine. The fillshoe is pushed forward until the delivery chute14 is centered above the die cavity 32. As the fillshoe is pushedforward, the powder is fluidized by turning the gas pressure on.

[0150] The powder is dropped in the die cavity 32 and the fillshoe isthen retracted. The fillshoe may dwell on top of the die cavity 32 foraround one second, depending on the size of the die cavity. Other filltimes are possible, but the preferred ranges are from 0.10 to 0.5seconds, 0.5 seconds to 1.0 seconds, and 1.0 to 3.0 seconds.

[0151] Powder overfills the die cavity 32 and as the fillshoe isretracted the front of the delivery chute 14 scrapes the top of the diecavity and levels the powders. Typically, the gas pressure is turned offafter the dwell time and during retraction of the fillshoe. However thegas may merely be run at a reduced pressure so as to substantiallylessen or completely reduce the powder flow without completely closingthe valves.

[0152] Once the gas pressure is off, all powder within the fillshoereturns to a state resembling a solid. During the next fill operation,the powder will have to be fluidized again before filling. The system ina preferred embodiment delivers an amount of powder for each filloperation enough to fill, or slightly overfill, the die cavity 32 andthen is turned off, as opposed to a continuous fill operation. However,in some circumstances a continuous fill may be desirable, e.g. inextremely high speed operations.

[0153]FIG. 3 shows a delivery chute 102 with a ring fluidizerconfiguration, S porous distributor plate 105 lies within the outer ring106 on the delivery chute 102. An inlet gas port 108 is provided forreceiving a compressed gas between the porous distributor plate 105 andthe outer ring 106.

[0154] A plurality of gas ports are present spaced radially around thering in a preferred embodiment. The porous distributor plate 105 ensuresuniform transmission of gas pressure to all sections of the deliverychute 102.

[0155] A powder ring around the porous distributor plate 105 inside thedelivery chute 102 becomes fluidized by migration of the gas through theporous distributor plate 105 and into the delivery chute 102. The powderis fluidized just before it drops inside the die cavity 110. Ventingscreens 112 are provided to allow the gas to escape and prevent buildupof pressure inside the delivery chute 102. The inclination of the porousdistributor plate 105 to the horizontal varies from zero (horizontal) to90 degrees (vertical) depending on the powder flow characteristics andpart shape, including size and complexity. Preferred ranges are from10-45 degrees, 45-90 degrees, and especially about 45 degrees.

[0156]FIG. 4A illustrates a delivery chute 102 with both a fluidizedvalve and ring fluidizer. The fluidized valve is used to meter thepowder flow into the die cavity 110 by turning the gas flow on and off.The fluidized valve consists of an individual fluidizer 114 combinedwith an extended collimator 116. The collimator 116 extends inside thedelivery chute leaving a gap D3 between the base of the collimator tube116 and the top of the porous distributor plate 104. When the gas isoff, the powder 120 in the collimator 116 and above the porousdistributor plate 104 forms a lock preventing any powder flow out of thedelivery chute.

[0157] The functioning of the fluidized valve depends on properformation of a powder lock as soon as the gas is shut off. The powderlock illustrated in FIG. 4A depends on the powder characteristics,especially the powder angle of repose, the diameter D1 of the collimatortube 116, the diameter D2 of the porous distributor plate 104 and thegap D3. An angle beta is defined such that the tangent of beta is equalto D3 divided by (D2−D1)/2 (see graphical representation 1 below). Ifthe angle beta is greater than the angle of repose of the powder, thanno powder lock will form. D2 is typically controlled by the insidediameter of the part to be compacted. D1 is fixed for a given deliverychute. D3 can be adjusted to enable a powder lock.

[0158] Typically, the angle beta is reduced to less than or equal to theangle of repose of the powder. At the same time, the gap controls thepowder flow rate out of the delivery chute. If the gap D3 is reducedsignificantly, the performance of the fillshoe will be adverselyaffected. The gap D3 should be as large as possible to increase powderflow rate when the gas is turned on while maintaining a powder lock whenthe gas is shut off. When the gas is turned on, the powder flows asillustrated in FIG. 4B.

[0159] Typical operation of the fluidized fillshoe with a singlefluidized valve has one major difference from the design with multiplefluidizers. While the gas is turned off, the fillshoe is pushed forwarduntil the delivery chute 122 is centered above the die cavity 124. Nopowder is dropped in the die cavity as the fillshoe is pushed forward.Once the delivery chute 122 is centered above the die cavity 124, thegas is turned on and the die cavity 124 is filled. As such, all powderis dropped vertically, consistently and uniformly into the die cavityduring successive filling operations.

[0160] The dwell time of the fill shoe over the die cavity 124 dependson the size of the die cavity 124. The gas is shut off, a powder lock isformed inside the collimator tube 126, and then the fill shoe isretracted. The dwell time is controlled with the timer to minimize theamount of overfill of the die cavity 124. As the fillshoe is retracted,the die cavity surface is scraped and the excess loose powder within thedelivery chute 122 is discharged into a cavity or sloped area in a wearplate on top of the die casting machine. As such, during the subsequentfill operation no residual powder exists within the delivery chute andno powder is dropped in the die cavity 124 during fillshoe movement.

[0161] Turning now to FIGS. 5A and 5B, a preferred apparatus for opencavity will be described in detail.

[0162] “Open cavity” refers to a set up in which there is a gap or openspace between the apparatus for powder/particulate material filling andthe cavity or container receiving the powder/particulate material.

[0163] Typically, powder/particulate material is delivered to a fillingstation above the container and dropped freely into an open container.Air in the container is allowed to escape freely. In this application,the fill system is stationary. When located on a production line, thereis generally no limit on space above the open cavity.

[0164] With reference to FIG. 5A particularly, a powder delivery andfilling system for an open cavity includes a mini-hopper 128, atransport 130, a delivery chute 132 and a gas control unit (not shown,but similar to FIG. 1B). The mini-hopper 128 has a porous distributorplate 134 for partitioning the mini-hopper into a first partition 136 inwhich the bed of particulate material is received and a second partition138 separate from the first partition and in communication with thefirst partition via the porous distributor plate 134.

[0165] An inlet powder port 140 is provided for receiving powdermixture/particulate material in the first partition. The inlet powderport 140 is connected to the main hopper with a leveling pipe 142. Thepowder flows through the inlet powder port 140 into the leveling pipe142 into the first partition 136 of the mini-hopper. When the powderlevel in the min-hopper 136 reaches the base of the leveling pipe 142the powder forms a lock, powder flow stops and the powder level ismaintained constant.

[0166] The powder flow resumes as soon as powder is discharged from themini-hopper 128 into the transport 130. An inlet gas port 144 isprovided for receiving a compressed gas in the second partition of themini hopper 128. The porous distributor plate 134 ensures uniformtransmission of gas pressure to all sections of the mini-hopper 128. Aselsewhere, the porous distributor plate may be either vertical or at anangle to the vertical, depending on powder flow characteristics.

[0167] As noted above, the layer of powder near the porous distributorplate 134 becomes loose by migration of the compressed gas through theporous distributor plate and into the first partition. The mesh size ofthe porous distributor plate 134 depends on the particle sizedistribution of the powder/particulate material, and is chosen toprevent clogging by entrapment of the small particles within the pores.

[0168] The mesh material is preferably stainless steel to provide highstrength, good wear properties, good weldability and non-corrosiveness.Other materials may be selected for varying purposes, e.g. filtering orthe like, and other materials may be used such as aluminum, copper,reinforced felting, etc.

[0169] The fluidization is controlled by regulating the gas pressure tothe inlet port 144. The volume of the gas flow and the gas pressure isimportant to the proper performance of the fill system. The gas pressureused depends on the powder characteristics and preferably should be keptat a minimum. The use of low gas pressure ensures that only the layer ofthe powder near the porous distributor plate 134 is fluidized while themajority of the powder remains in a solid state.

[0170] This will prevent powder segregation in the mini-hopper 128 whenusing a powder mixture with a wide powder size distribution, prevent anydusting of fine particles, and the powder can maintain a lock around theinlet leveling pipe 142.

[0171] Turning now to FIG. 5B, it can be seen that the mini-hopper 128is covered with a venting screen 148 which allows the gas to escape toprevent build up of pressure within the mini-hopper while entraining anyparticles. The mesh size of the venting screen 148 depends on theparticle size distribution of the powder/particulate material beingused.

[0172] The mini-hopper 128 provides a break between the fillshoe and themain hopper. As such, it advantageously isolates the filling operationfrom the variations in head pressure, and provides a constant powderhead. The result is to maintain uniform conditions for successive filloperations, which contributes to consistency of fill.

[0173] The transport device 130 has a porous distributor plate 152 forpartitioning the transport into a first partition 154 in which theparticulate material is received and a second partition 156 separatefrom the first partition and in communication with the first partitionvia the porous distributor plate 152. An inlet gas port 158 is providedfor receiving a compressed gas in the second partition.

[0174] The porous distributor plate 152 ensures uniform transmission ofgas pressure to the first partition of the fluidized pipe transportdevice 154. The layer of powder near the porous distributor plate 152becomes loose by migration of the compressed gas through the porousdistributor plate and into the first partition. Again, the mesh size ofthe porous distributor plate 152 depends on the particle sizedistribution of the powder/particulate material, and is chosen toprevent clogging by entrapment of the small particles within the pores.

[0175] The mesh material is preferably stainless steel to provide highstrength, good wear properties, good weldability and is non-corrosive,but other materials may be used.

[0176] The fluidization is controlled by regulating the gas pressure tothe inlet port 158. The magnitude of the gas pressure is important tothe proper performance of the fill system. The gas pressure used dependson the powder characteristics and should be kept at a minimum. The useof low gas pressure ensures that only a thin layer of the powder nearthe porous distributor plate 152 is loosened to eliminate or minimizedusting and segregation.

[0177] The transport 130 is covered with a venting screen 160 whichallows the gas to escape to prevent build up of pressure whileentraining any particles. The mesh size of the venting screen 160depends on the particle size distribution of the powder/particulatematerial being used. The inclination of the porous distributor plate 152to the horizontal varies depending on powder flow characteristics. Atypical inclination is around 45 degrees, but ranges from 5-25; 25-65;and 65-75 are possible depending on the powder type.

[0178] The delivery chute 132 functions as the powder discharge unitdirectly above the open cavity 164. The delivery chute 132 has acollimator pipe 166 and a fluidizer 169. The collimator pipe 166redirects the direction of flow of the powder to vertical and isdirectly positioned above the open cavity.

[0179] The fluidizer 169 has the same design as the fluidizerillustrated in FIGS. 4A and 4B. The combination of the collimator pipe166 and fluidizer porous distributor plate 168 enable the system tofunction as a fluidized valve with powder flow when the gas is turned onand no powder flow when the gas is turned off.

[0180] The delivery chute 132 is covered with a venting screen 170 whichallows the gas to escape to prevent build up of pressure within thedelivery chute 132 while entraining any particles. The mesh size of theventing screen 170 depends on the particle size distribution of thepowder/particulate material being used. The proximity of the ventingscreen 170 to the top of the porous distributor plate 168 is critical toallow the gas to escape in the least amount of time to prevent anyturbulence caused by buildup of gas pressure and interference withpowder flow within the collimator tube 166.

[0181] An inlet gas port 172 is provided for receiving a compressed gasin the fluidizer.

[0182] The gas control unit 16 as illustrated in FIG. 1B is located in aseparate housing and is used to control the gas moisture content andregulate powder fluidization timing in relation to time of filling ofthe open container. The gas control unit 16 is used to regulate the flowof gas to each segment of the fillshoe system independently. The timingof the gas flow to the center fluidizer is used to meter the amount ofpowder discharged into the cavity 164.

[0183] The gap D3 between the base of the collimator tube 166 and thetop of the porous distributor plate 168 is adjusted to control the flowrate. When the gas is off, the powder in the collimator 166 and theporous distributor plate 168 forms a lock preventing any powder flow outof the delivery chute 132.

[0184] The functioning of the fillshoe system depends on properformation of a powder lock as soon as the gas is shut off. The powderlock illustrated in FIG. 5A depends on powder characteristics,especially the powder angle of repose, the diameter D1 of the collimatortube 166, the diameter D2 of the porous distributor plate 168 and thegap D3. An angle beta is defined such that the tangent of beta is equalto D3 divided by (D2−D1)/2. If the angle beta is large than no powderlock will form. D2 is typically controlled by the inside diameter of thepart to be compacted. D1 is fixed for a given delivery chute. D3 can beadjusted to enable a powder lock.

[0185] Typically, the angle beta is reduced to less than or equal to theangle of repose of the powder. A preferred angle is 45 degrees, andother usuable ranges include 25-65 degrees and from 10-80 degrees,approaching the vertical or horizontal. At the same time, the gapcontrols the powder flow rate out of the delivery chute. If the gap isreduced significantly, the performance of the fill system will beadversely affected. The gap D3 should be as large as possible whilemaintaining a powder lock.

[0186] When the gas is turned on, the powder flows as illustrated inFIG. 5B. A built in micrometer 174 is used to adjust the gap D3. Themicrometer 174 is near the gap D3 which makes it easy to use, and is onthe outside the delivery chute 132 which makes it easy to access.

[0187]FIG. 6 illustrates one method for supporting the apparatus forfilling open cavities. The apparatus may be affixed to post 176

[0188]FIG. 7 illustrates an embodiment suitable for powder/particulatematerial with very poor flow characteristics. A fluidized cone 178 isintroduced between the transport 180 and the delivery chute 182. Thefluidized cone 178 has a porous distributor plate 184 for partitioningthe fluidized cone 178 into a first partition in which the particulatematerial is received and a second partition separate from the firstpartition and in communication with the first partition via the porousdistributor plate 184.

[0189] An inlet gas port 186 is provided for receiving a compressed gasin the second partition. The layer of powder near the porous distributorplate 184 becomes loose by migration of the compressed gas through theporous distributor plate and into the first partition. The fluidizationis controlled by regulating the gas pressure to the inlet gas port 186.The magnitude of the gas flow and the gas pressure is important to theproper performance of the fill system.

[0190] The gas pressure used depends on the powder characteristics andshould be kept at a minimum. The use of low gas pressure ensures thatonly a thin layer of the powder near the porous distributor plate 184 isloosened to eliminate or minimize dusting and segregation. The conefluidizer 178 is covered with a venting screen 188 which allows the gasto escape to prevent build up of pressure while entraining anyparticles.

[0191] The inclination of the porous distributor plate 184 to thehorizontal varies depending on powder flow characteristics. A typicalinclination is around 45 degrees.

[0192] Turning now to FIG. 8, an embodiment suitable forpowder/particulate material with poor flow characteristics is described.With such characteristics, replenishment of the mini-hopper from themain hopper through a flexible hose may be inconsistent. An in-linefluidized connector is introduced at discrete locations along theflexible tube, especially at the location where there is a reduction inthe diameter of the tube.

[0193] The purpose of the fluidized connector is to assist powder flowin pipes and tubes, especially at areas with a transition in pipediameter. With reference to FIG. 8, a porous distributor plate 190surrounds the outer ring 192 of the fluidized connector 194. An inletgas port 196 is provided for receiving a compressed gas between theporous distributor plate 190 and the outer ring 192. A powder ringaround the porous distributor plate 190 inside the fluidized connector194 becomes fluidized by migration of the gas through the porousdistributor plate 190 and into the fluidized connector 194.

[0194] Venting screens 198 are provided to allow the gas to escape andprevent buildup of pressure inside the fluidized connector or exitthrough the inlet pipe 200 or the outlet pipe 202. The inclination ofthe porous distributor plate 190 to the horizontal is 45 degrees, but isadjusted depending on the powder flow characteristics.

[0195] The control of gas pressures, volumes, and flow to the variousgas inlet ports of the present invention is controllable by variablevalves as illustrated in FIG. 1B. The valves may be controlled by acomputer running appropriate software to accomplish the result of smoothflow. The valves may also be manually adjusted by an experiencedoperator for smooth flow. Suitable computer equipment includesstandalone or networked computers for control of stages of a continuousprocess. Strategically located sensors may detect excess powder flow,and optical inspection may reveal insufficiently filled dies or molds.In that event, the sensors, which can be linked to the control computer,signal that too much or too little powder is being transferred thoughthe apparatus, and the gas flow may be increased or decreased as thesituation warrants.

[0196] While the invention has been particularly shown and describedwith reference to a preferred embodiment thereof, it will be understoodby those skilled in the art that various changes in form and details maybe made therein without departing from the spirit and scope of theinvention.

What we claim:
 1. A method of transporting particulate materials througha transfer pipe by means of gravity flow including the steps of passingsaid particulate material through a fluidized connector of the type inwhich said fluidized connector is partitioned by a porous distributorplate to form first and second chambers and wherein the particulatematerials pass through said first chamber which is in gaseouscommunication with said second chamber via said porous distributorplate, said method comprising the steps of: delivering gas to saidsecond chamber at a pressure sufficient to generate a gas bearingbetween said porous distributor plate and said particulate material butto permit said gas to migrate through said particulate material to ventsaid gas to the surrounding atmosphere without causing substantialturbulence in said particulate material and to reduce tendencies fordusting and separation of the particulates into sizes.
 2. The method ofclaim 1 includes the step of determining the porosity of saiddistributor plate in accordance with the type of particulates passingover said porous distributor plate.
 3. The method of claim 1 includingthe step of adjusting said gas flow in accordance with thecharacteristics of said particulate material passing through said firstchamber.
 4. The method of claim 1 including the step of adjusting saidgas flow in accordance with the lubrocity of said particulates.
 5. Themethod of claim 1 including the step of removing dust particles fromsaid gas that migrates through said particulate materials.
 6. The methodof claim 1 wherein said first chamber has an upstream end and adownstream end and includes the step of increasing the cross-sectionalarea of said first chamber at its downstream end.
 7. The method of claim1 wherein said transfer pipe has a first end and a second end andwherein said first end is located vertically above said second end andsaid method includes the step of adjusting the flow of said gas inaccordance with the height of said first end relative to said secondend.
 8. The method of claim 7 including the step of adjusting the heightof said first end relative to said second end.
 9. The method of claim 1for use in combination with a die-casting machine of the type in which acavity is located below a die punch by a given distance, and whereinsaid transfer pipe has a first end and second end, said method includingthe step of: adjusting the height of said first end relative to saidsecond end in accordance with the height of said punch above said diecavity.
 10. The method of claim 1 for use in combination with a systemcomprising a plurality of said fluidized connectors wherein each saidfluidized connector has a source of gas, said method including the stepof separately adjusting the gas flow from each of said gas sources. 11.A method of filling a die cavity in a die casting machine with aparticulate material comprising the steps of: moving aparticulate-filled delivery chute over said die cavity; fluidizing saidparticulate material with pressurized gas while simultaneously ventingsaid gas to atmosphere to reduce turbulation of said particulatematerial; using gravity flow to overfill said cavity with saidparticulate material; retracting said delivery chute from above said diecavity while scraping the overfill of said particulate material fromabove said die-cavity; and, terminating said fluidized gas pressure. 12.Fuidizing apparatus for filling a cavity with a homogeneous dispersionof a particulate material comprising: a hopper, a transport section, anda deliver chute; said hopper being located above a horizontal plane andadapted for containing particulate material, said hopper having an upperportion, a lower portion, and a plurality of sides; said transportsection being operative to transport said particulate material from saidhopper to said delivery chute and having an upper end and a lower endand connected at said upper end to a side of said hopper and descendingat an angle to said horizontal plane to said lower end connected to saiddelivery chute; said delivery chute having an upper portion and a lowerportion and connected at said upper portion to said lower end of saidtransport section to deliver said particulate material from saidtransport section to said cavity; a porous distributor plate located insaid lower portion of said hopper to partition said hopper into a firstchamber in which said particulate material is stored and a secondchamber in gaseous communication with said first chamber via said porousdistributor plate; a vent located in said upper portion of said hopper;a compressed gas source connected to said porous distributor plate fordelivering said gas to said second chamber, the pressure of said gasbeing such that said gas provides a gas bearing between said porousdistributor plate and said particulate material and then migratesthrough said particulate material and out of said vent to fluidize saidparticulate material without causing turbulence in the majority of saidparticulate material.
 13. The fluidizing apparatus of claim 12, for usewith a die-casting machine having a die cavity therein and an entry tothe die cavity located on an upper surface of said die, said openinghaving a given cross-sectional shape; said lower end of said deliverychute being adapted to engage said opening at said upper surface of saiddie and having a cross-section at said lower end having a shapecorresponding to said shape of said opening of said die.
 14. Thefluidized apparatus of claim 13 wherein said die cavity has at least oneshallow-depth portion and at least one deeper-depth portion, saidfluidized system including a fillshoe having a filling position and anonfilling position; at least one distributor plate having a centralportion and an outer portion from which, when said fillshoe is in saidfilling position, said particulate material is dropped by gravity intosaid die cavity located therebelow; said central portion being located,when said fillshoe is in said filling position, above said shallow-depthportion of said die cavity; and, said outer portion, when said fillshoeis in said filling position, being located above said deeper-depthportion so that said particulate material drops into said deeper-depthportion.
 15. The fluidizing apparatus of claim 14 wherein said diecavity has a plurality of said shallow-depth portions and a plurality ofsaid deeper-depth portions and wherein said fillshoe further includes aplurality of said distributor plates each having a said central portionand a said outer portion; and, wherein said central portions of saiddistributor plates, when said fillshoe is in said filling position, arelocated above said shallow-depth portions of said die cavity; and, saidouter portions of said distributor plates, when said fillshoe is in saidfilling position, are located above the deeper-depth portions so thatsaid particulate material drops into said deeper-depth portions.
 16. Thefluidizing apparatus of claim 14 wherein said porous distributor platehas a second side and a first side for receiving particulate materialthereon; and, a source of gas delivered to said second side of saidporous distributor plate with said gas having a pressure such that a gasbearing is formed between said first side of said porous distributorplate and the particulates located thereon, so that said gas migratesthrough said particulate material, but permits said particulate materialto move off of said first side of said porous distributor plate and thendrops by gravity into said deeper-depth portion.
 17. The fluidizingapparatus of claim 12 including a gas-control unit for regulating thepressure of said gas to insure the existence of said gas bearing and theabsence of turbulence in said majority of said particulate material. 18.The fluidizing apparatus of claim 12, wherein said transport section hasa first portion and a second portion and includes a second porousdistributor plate located in said first portion of said transportsection to partition said transport section into a firsttransport-section chamber through which said particulate materialtravels and a second transport-section chamber in gaseous communicationwith said first transport-section chamber via said second porousdistributor plate; and, a transport section vent located in said firstportion of said transport section; and, a gas inlet for delivering gasto said second transport-section chamber to provide a gas bearingbetween said second porous distributor plate and said particulatematerial located in said transport section, said gas migrating throughsaid particulate material and out of said transport-section vent withoutcausing turbulence in the majority of said particulate material in saidtransport section.
 19. The fluidizing apparatus of claim 18, whereinsaid delivery chute includes a delivery-chute vent located in said upperportion of said delivery chute, a third porous distributor plate forpartitioning said delivery chute into a first delivery-chute chamberthrough which particulate material is passed and a second delivery-chutechamber in gaseous communication with said first delivery chute chambervia said third porous distributor plate; and, a compressed gas sourceconnected to said third porous distributor plate for deliveringcompressed gas to said second delivery-chute chamber the pressure ofsaid gas being such that said gas provides a gas bearing between saidthird distributor plate and said particulate material and then migratesthrough said particulate material in said delivery chute and out of saiddelivery-chute vent without causing turbulence in the majority of saidparticulate material located in said delivery chute.
 20. The fluidizingapparatus of claim 12, wherein said delivery chute includes adelivery-chute vent located in said upper portion of said deliverychute, a second porous distributor plate for partitioning said deliverychute into a first delivery-chute chamber through which particulatematerial is passed and a second delivery-chute chamber in gaseouscommunication with said first delivery chute chamber via said secondporous distributor plate; and a compressed gas source connected to saidsecond pourous distributor plate for deliverying compressed gas to saidsecond delivery-chute chamber, the pressure of said gas delivered tosaid second delivery-chute chamber being such as to provide a bearingbetween said second distributor plate and said particulate material andthen migrates through said particulate material in said delivery chuteand out of said delivery-chute vent without causing turbulence in themajority of said particulate material located in said delivery chute.21. Fluidizing apparatus for containing particulate material to bedelivered therefrom by gravity flow, said fluidizing system comprising:an upper portion and a lower portion of said fluidizing system fromwhich said particulate material exits by gravity flow; a porousdistributor plate for partitioning said fluidizing system into a firstchamber in which said particulate material is stored and a secondchamber in communication with said first chamber via said porousdistributor plate; a vent located in said upper portion of saidfluidizing system; a source of compressed gas connected to said secondchamber wherein the pressure of said gas is such as to provide a gasbearing between said porous distributor plate and said particulatematerial in said first chamber and wherein said gas migrates throughsaid particulate material and out of said vent without causingturbulence in the majority of said particulate material.
 22. Fuidizingapparatus including a fluidized connector having an inlet end and anoutlet end for connection between an inlet portion and an outlet portionof a transport for transporting particulate materials; a porousdistributor plate located within said fluidized connector to partitionsaid fluidized connector into a first chamber through which saidparticulate material is passed and a second chamber in communicationwith said first chamber via said porous distributor plate; a source ofgas connected to said second chamber for delivering said gas to andthrough said porous distributor plate; and, a vent for venting said gasfrom said first chamber; the pressure of said gas in said second chamberbeing such as to be provide a gas bearing between said porousdistributor plate and said particulate material in said first chamber,said gas then migrating through said particulate material and out ofsaid vent without causing turbulence within the majority of saidparticulate material.
 23. The fluidizing apparatus of claim 22, whereinsaid vent essentially covers the upper portion of said fluidizedconnector to maximize the venting of said gas which migrates throughsaid particulate material to further reduce tendencies for turbulencewithin said particulate material.